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NMSU researchers compete for spot on Space Station

Researchers at New Mexico State University's R.L. Golden Particle Astrophysics Laboratory are competing for a coveted spot on an elite international team -- the International Space Station.

"One of the payload points on the International Space Station has been designated for a cosmic ray experiment," said Steven Stochaj, director of the Particle Astrophysics Lab. "NASA is having a kind of competition to come up with the best detectors to put on the Space Station."

With $250,000 in NASA funding over two years, Stochaj and his colleagues are designing a detector for measuring the energy of cosmic rays in space. It's based on an instrument that already has proved itself on several high-altitude scientific balloon flights the lab has launched to study cosmic rays from near-space.

Four other proposals also have been funded by NASA and ultimately one will be selected to be taken into orbit via Space Shuttle and attached to the International Space Station, a joint venture of the United States, Russia and other nations. Deployment of the cosmic ray experiment, known as ACCESS (Advanced Cosmic Ray Composition Experiment for the Space Station), is scheduled for 2005.

From its vantage point in orbit, the Space Station will allow space scientists to do long-term experiments outside the Earth's atmosphere and the distortions it can cause. That can be especially useful in the study of cosmic rays, which may hold important clues to the way the universe is evolving.

"The ultimate goal of astrophysics is to learn how the universe works," Stochaj said. Among other things, he said, "the study of cosmic rays gives us a better understanding of the dynamics of supernova explosions."

The origin of cosmic rays remains uncertain, but scientists believe some of them are fueled by supernova explosions, which occur when a massive star dies and its outer layers blast into space. To measure cosmic rays before they interact with the earth's atmosphere, the Particle Astrophysics Lab sends instruments by balloon high into the stratosphere, where they can measure the energy and velocity of cosmic ray particles and determine their chemical composition and origins.

Some of the particles, especially those with the highest energy levels, are much scarcer than others. "You can't see enough of them in a one- or two-day balloon flight to get good data," Stochaj said.

The cosmic ray experiment slated for the Space Station, however, is a three- to five-year mission. The detectors that will be attached to the Space Station will be especially sensitive to high-energy particles and the long exposure time will give scientists much more information to work with, Stochaj said.

Collaborating with Stochaj on the ACCESS project are Italian scientists who are involved in the Particle Astrophysics Lab's high-altitude balloon research. At least one NMSU graduate student also will participate in the project.

The instrument the group is developing, known as a calorimeter, utilizes layers of tungsten and strips of silicon. As cosmic ray particles pass through the tungsten, the interaction registers in the silicon. From the instrument's readings, the scientists can measure the charge and energy level of each particle.

The group developed a similar silicon strip calorimeter for its balloon-borne experiments. On the most recent flight, in June, the scientists were able to record for the first time ever the collision and annihilation of a proton and a cosmic ray anti-proton. Matter and anti-matter particles, which have opposite electrical charges, annihilate each other when they meet.

The late Robert L. Golden, founder of NMSU's Particle Astrophysics Laboratory, was the first to discover naturally occurring antimatter, in 1979. He used a giant helium-filled balloon, similar to the ones used today by the lab's researchers, to carry his specialized instruments to the top of the earth's atmosphere.

The Particle Astrophysics Laboratory is a unit of NMSU's College of Engineering.